The present invention relates to vehicular shock absorbers that are particularly suitable for use in snowmobiles and that have adjustable preloads applied to them by coil over springs.
The manufacture of components used in vehicles present unique and difficult challenges. Not only must the component be manufactured by mass production techniques to exacting, ever more demanding standards, but the costs of manufacturing must be minimized. The difference is fractions of a cent in the manufacturing cost is at times of importance to the acceptance of a component.
The weight of a component is also quite important particularly in components used on vehicles such as snowmobiles. For years, snowmobile manufacturers have sought to have component manufactures reduce the weight of their components so as to reduce the overall weight, and thus enhance the performance of a snowmobile. Again, even slight differences in weight are of importance and often a deciding factor in a snowmobile's manufacturer's decision to purchase a component.
Shock absorbers, which have adjustable preloads applied to them by means of coil over springs, are known and are used on snowmobiles. A shock absorber of this type is illustrated in and is indicated generally at 12 in FIG. 1. The conventional structure presently used to adjust the preloads on such shock absorbers includes an annular aluminum casting, shown at 14 in FIG. 1, that is slid over and mounted on the reservoir tube, shown at 16, of the shock absorber. A plastic adjusting nut, shown at 18 in FIG. 1, is threaded on radially outwardly facing threads on the aluminum casting 14. The lower end 22 (as seen in FIG. 1) of the coil over spring 24 abuts the adjusting nut 18. A plurality of spaced apart, radially outwardly projecting dimples 26, which are formed on the wall of the reservoir tube 16, served to hold the aluminum casting 14 axially and against rotation with respect to the reservoir tube. Rotation of the adjusting nut 18, with respect to the aluminum casting 14, results in an increase or decrease of the preload or bias applied by the coil over spring 24.
While the above prior art coil over spring adjustment structure was and is capable of adjusting satisfactorily the coil over spring applied preload, this structure has several commercially significant drawbacks. First, it requires two parts, the aluminum casting 14 and the adjusting nut 18. The casting, even though made of aluminum, is relatively heavy and adds weight to the shock absorber 12. Further, because the radial thickness of the annular aluminum casting 14, the I.D. of the coil over spring 24 must be greater than otherwise would be required for the spring to function as intended.
As might be expected, shock absorber manufacturers, as well as others in the snowmobile industry, have long sought a better, lighter weight and less costly structure for adjusting the preload applied by coil over springs to otherwise conventional shock absorbers.